M&S says

For plenty of comfort while you sleep or lounge, our supremely washable square pillow will have you feeling relaxed and totally indulged. Made with a comfy polyester Dacron filling, this handy pillow is simple to wash and dry while always maintaining its original shape, so you can easily have it laundered in just a few hours, should any unexpected spills occur. With a highly breathable, moisture-wicking, non-allergenic makeup, this great pillow keeps you dry and comfortable all night long.